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18 pages, 7838 KiB

Open AccessArticle

Environmental Implications of the Soil-to-Groundwater Migration of Heavy Metals in Mining Area Hotspots

by Jelena Vesković and Antonije Onjia

Metals 2024, 14(6), 719; https://doi.org/10.3390/met14060719 - 17 Jun 2024

Cited by 3 | Viewed by 1834

Abstract

Groundwater contamination was studied at several hotspot sites in the Majdanpek copper mining area (Serbia). These sites include a milling facility, a metallurgical wastewater treatment plant, a heavy vehicle service area, and a waste disposal site. In addition to Cu, high concentrations of [...] Read more.

Groundwater contamination was studied at several hotspot sites in the Majdanpek copper mining area (Serbia). These sites include a milling facility, a metallurgical wastewater treatment plant, a heavy vehicle service area, and a waste disposal site. In addition to Cu, high concentrations of As and heavy metals (Cd and Pb) were detected in groundwater and soil at the same sampling points. Mining operations and heavy vehicle transport activities have been identified as the main sources of pollution. The migration of metals from soil to groundwater, expressed as a concentration ratio, were the highest for Co and the lowest for Mn. The environmental implications of groundwater pollution were studied using the heavy metal pollution index (HPI), Nemerov pollution index (NPI), hazard index (HI), and incremental lifetime cancer risk (ILCR). HPI and NPI show the high potential of groundwater to have adverse environmental effects. HPI ranges in the following descending order of metals: Cd > Pb > As > Mn > Ni > Cr > Hg > Cu > Zn. NPI exceeds the threshold of 0.7 in 66.7% of the samples. Potential human exposure to the studied groundwater may cause severe health problems in adults, with HI ranging from 0.61 to 5.45 and ILCR from 1.72 × 10⁻⁴ to 1.27 × 10⁻³. Children were more susceptible to non-carcinogenic risk than adults, with HI ranging from 0.95 to 8.27. However, the results indicated that children were less prone to carcinogenic risks, with ILCR ranging from 5.35 × 10⁻⁵ to 3.98 × 10⁻⁴. Arsenic is the most contributing element to both risks. This research imposes the need for enhanced groundwater monitoring at hotspots in the mining area and the adoption of remediation plans and measures. Full article

(This article belongs to the Special Issue Comprehensive Utilization of Metallurgical Resources and Environmental Protection)

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11 pages, 4789 KiB

Open AccessArticle

Harnessing Microwave Technology for Enhanced Recovery of Zinc from Industrial Clinker

by Bagdaulet Kenzhaliyev, Tatiana Surkova, Ainur Berkinbayeva, Zhazira Baltabekova and Kenzhegali Smailov

Metals 2024, 14(6), 699; https://doi.org/10.3390/met14060699 - 13 Jun 2024

Cited by 2 | Viewed by 873

Abstract

This article presents a cutting-edge approach to microwave-assisted processing aimed at enhancing the efficiency of zinc extraction from materials characterized by a high degree of processing complexity. The described technique encompasses two sequential phases: phase transformation under microwave irradiation and leaching in sulfuric [...] Read more.

This article presents a cutting-edge approach to microwave-assisted processing aimed at enhancing the efficiency of zinc extraction from materials characterized by a high degree of processing complexity. The described technique encompasses two sequential phases: phase transformation under microwave irradiation and leaching in sulfuric acid at ambient temperature. During the phase transformation, implemented through the application of microwave energy, insoluble zinc phases undergo a controlled transition. The experimental results confirm that microwave calcination at 600 °C for 5–7 min is effective for converting ZnS to ZnO without the formation of ZnO∙Fe₂O₃. Zinc extraction from the clinker reached 46.47% after treatment with microwave radiation at a power of 25 kW for the specified duration. Thus, this study opens up prospects for environmentally friendly zinc extraction from challenging-to-process resources. Full article

(This article belongs to the Special Issue Comprehensive Utilization of Metallurgical Resources and Environmental Protection)

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8 pages, 2874 KiB

Open AccessCommunication

Thermodynamics of Aluminothermic Processes for Ferrotitanium Alloy Production from Bauxite Residue and Ilmenite

by Dimitris Sparis, Adamantia Lazou, Efthymios Balomenos and Dimitrios Panias

Metals 2024, 14(2), 200; https://doi.org/10.3390/met14020200 - 6 Feb 2024

Viewed by 1385

Abstract

Titanium oxide is a major component of bauxite residue (BR) with a high value, but it is often an unwanted element in common BR reuse options such as cement or iron production. Conventional carbothermic reduction smelting of BR produces a slag still containing [...] Read more.

Titanium oxide is a major component of bauxite residue (BR) with a high value, but it is often an unwanted element in common BR reuse options such as cement or iron production. Conventional carbothermic reduction smelting of BR produces a slag still containing a large amount of Ti. This study investigates an aluminothermic process for producing an FeTi alloy by combining BR, ilmenite ore, and fluxes. Based on thermodynamic calculations and batch experiments, the amounts of aluminum (reductant) and fluxes were investigated to achieve the optimum alloy production in parallel with a slag that could be further valorized in the cement industry. The mineralogical and chemical analysis of the metallic and slag phase agreed with the thermodynamic calculations. The results obtained by this study can lead to the development of a new process for the complete valorization of BR, paving the way for scaling up aluminothermic processes for producing ferroalloys from all iron-rich residues. Full article

(This article belongs to the Special Issue Comprehensive Utilization of Metallurgical Resources and Environmental Protection)

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14 pages, 2729 KiB

Open AccessArticle

Effect of Thiourea on Lead Release from Lead-Bearing Jarosite under Freeze–Thaw Cycling

by Jun Peng, Hui Liu, Yujun Shen, Luhua He, Yangjin Wei and Xu Yan

Metals 2023, 13(6), 1053; https://doi.org/10.3390/met13061053 - 31 May 2023

Cited by 1 | Viewed by 1349

Abstract

Lead is a toxic factor in jarosite residue, and it is important to study its release behavior from simulated lead jarosite residue (LSJ) to predict the stability of the jarosite residue and its impact on the environment. This study investigated the ion release [...] Read more.

Lead is a toxic factor in jarosite residue, and it is important to study its release behavior from simulated lead jarosite residue (LSJ) to predict the stability of the jarosite residue and its impact on the environment. This study investigated the ion release behavior, leaching toxicity, stability, and ion migration of LSJ during freeze–thaw cycling with thiourea (T-FTC). The release of lead, iron, and sulfate radicals from lead jarosite via T-FTC was influenced by several factors. Under specific conditions, the amount of lead released was 6.09 mM/L, which accounted for 38.3% of the total lead. After the T-FTC treatment, the residual lead increased, and the leaching toxicity and long-term stable equilibrium concentration of lead were reduced to 42.1 mg/L and 12.4 mg/L, respectively, which decreased by 82% and 84%, respectively and led to improved environmental stability. This study provides a novel approach for the safe disposal of jarosite residue under low-temperature and mild conditions, and the results can be used to predict the stability of jarosite residue and its secondary pollution in the environment. Full article

(This article belongs to the Special Issue Comprehensive Utilization of Metallurgical Resources and Environmental Protection)

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15 pages, 4767 KiB

Open AccessArticle

The Synthesis of Lead-Bearing Jarosite and Its Occurrence Characteristic and Leaching Toxicity Evaluation

by Jun Peng, Luhua He, Hui Liu, Zhumei Sun and Xu Yan

Metals 2023, 13(5), 941; https://doi.org/10.3390/met13050941 - 12 May 2023

Cited by 3 | Viewed by 1377

Abstract

Lead is the main toxic factor in jarosite residue. It is important to study the release behavior of lead from simulated lead-bearing jarosite (SLBJ) for predicting the stability of jarosite residue and its secondary pollution to the environment. To identify the technical issues [...] Read more.

Lead is the main toxic factor in jarosite residue. It is important to study the release behavior of lead from simulated lead-bearing jarosite (SLBJ) for predicting the stability of jarosite residue and its secondary pollution to the environment. To identify the technical issues and limitations associated with its safe disposal, a comprehensive analysis of the chemical, structural, and morphological characteristics of SLBJ was conducted using various detection techniques including XRF, XRD, SEM-EDS, FTIR, XPS, etc. The environmental stability of SLBJ was assessed through the toxicity characteristic leaching procedure (TCLP), Chinese standard leaching tests (CSLT), and a long-term leaching experiment (LTLE). Phase composition analysis revealed that the primary components of SLBJ are sodium jarosite and lead sulfate. TCLP and CSLT results indicated that lead content surpassed the toxicity identification standard limit by more than 47 times. Furthermore, LTLE indicated that the lead concentration surpassed the standard limit about 15 times after prolonged contact time. This study is of great significance for predicting the stability of jarosite residue and its secondary pollution to the environment. Full article

(This article belongs to the Special Issue Comprehensive Utilization of Metallurgical Resources and Environmental Protection)

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10 pages, 1848 KiB

Open AccessArticle

Relation between Viscosity and Conductivity of CaO-MgO-FeO-Al₂O₃-SiO₂ System for Copper Smelting Slags

by Lei Zhang, Kaixi Jiang, Feng Xie and Diankun Lu

Metals 2023, 13(4), 786; https://doi.org/10.3390/met13040786 - 17 Apr 2023

Cited by 1 | Viewed by 1489

Abstract

The viscosity and conductivity of the smelting slag of copper oxide concentrate are important for reducing the operating temperature. In this study, seven slag samples were prepared by the reductive smelting of copper oxide concentrate with different ferrous oxide contents. The viscosity and [...] Read more.

The viscosity and conductivity of the smelting slag of copper oxide concentrate are important for reducing the operating temperature. In this study, seven slag samples were prepared by the reductive smelting of copper oxide concentrate with different ferrous oxide contents. The viscosity and conductivity data of these CaO-MgO-FeO-Al₂O₃-SiO₂ samples were measured in the temperature range of 1290~1410 °C. Based on the structural features of aluminosilicate melts, the change and dependency relationships of their viscosity and conductivity were analyzed. The results show that there is a strong tendency to form orthosilicate even when the slag composition is acidic. The formation of fayalite would allow more Al³⁺ to form pyroxene with the six-coordinated structure. As a result, the polymerization degree and viscosity of the melt will be reduced. The

{[AlO]}_{4}^{5 -}

as a network former will reduce the bonding strength of the structural units, thus reducing the slag viscosity at high temperature. In the experimental range, the logarithm of viscosity of each slag sample has a good linear relationship with its logarithm of conductivity. However, there is no uniform linear equation for these complex slags with wide composition variations. These results have potential guiding significance for the copper smelting process. Full article

(This article belongs to the Special Issue Comprehensive Utilization of Metallurgical Resources and Environmental Protection)

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13 pages, 8318 KiB

Open AccessArticle

Preparation of Black Ceramic Tiles with Chromium Slag and Copper Smelting Waste Slag

by Yanglai Hou, Jiajie Yu, Zhiqiao Li, Yuanhao Hai, Ju Xu and Dingli Zheng

Metals 2023, 13(3), 537; https://doi.org/10.3390/met13030537 - 7 Mar 2023

Cited by 1 | Viewed by 1336

Abstract

Chromium slag and copper smelting waste slag are solid wastes generated in the process of industrial production of chromium salt and copper metal, respectively. In this study, chromium slag and copper smelting waste slag were used as raw materials to produce black ceramic [...] Read more.

Chromium slag and copper smelting waste slag are solid wastes generated in the process of industrial production of chromium salt and copper metal, respectively. In this study, chromium slag and copper smelting waste slag were used as raw materials to produce black ceramic tiles. It can not only reduce environmental pollution but also increase their utilization value. The chromaticity values of ceramic tiles (L*, a*, and b*), which are color models developed by the International Commission on Illumination, were measured using a colorimeter. The phases and microstructure of the ceramic tile were analyzed by X-ray diffractometer (XRD), scanning electron microscope and energy-dispersive X-ray spectrometry (SEM-EDS), respectively. The effects of different process parameters on the coloring performance of ceramic tiles were also investigated. The results show that the color of ceramic tile is the best when the Fe/Cr ratio is 1.5, the sintering temperature is 1200 °C, the holding time is 30 min and the ceramic tile is cooled in the furnace. The values of L*, a*, and b* are, respectively, 22.5, 0, and −1.6. The compressive strength of ceramic tile and the leaching concentration of Cr(VI) are 127.2 MPa and 3.31 mg/L, respectively, which can meet the relevant national standards. Full article

(This article belongs to the Special Issue Comprehensive Utilization of Metallurgical Resources and Environmental Protection)

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13 pages, 34795 KiB

Open AccessArticle

Microwave Drying Kinetics of Chromium-Rich Electroplating Sludge

by Jian Zhang, Zhiwei Peng, Guanwen Luo, Ran Tian and Mingjun Rao

Metals 2023, 13(1), 87; https://doi.org/10.3390/met13010087 - 30 Dec 2022

Cited by 6 | Viewed by 1606

Abstract

Chromium-rich electroplating sludge (CRES) is a hazardous solid waste with a high content of moisture requiring efficient drying before subsequent treatment. In this study, the microwave drying kinetics of CRES were examined. The results showed that CRES had good microwave absorptivity, contributing to [...] Read more.

Chromium-rich electroplating sludge (CRES) is a hazardous solid waste with a high content of moisture requiring efficient drying before subsequent treatment. In this study, the microwave drying kinetics of CRES were examined. The results showed that CRES had good microwave absorptivity, contributing to a much shorter drying time and better drying performance compared with conventional drying. In comparison with conventional drying at 105 °C, the time of microwave drying at 600 W for total moisture removal was reduced by 98.5%. Compared to load mass and particle size, microwave power played a more important role in microwave drying. Based on the kinetics analysis, the microwave drying process of CRES could be divided into three successive stages, in which the drying rates were limited by external diffusion (before 110 s), both external diffusion and chemical reaction (between 110 s and 160 s), and chemical reaction (after 160 s), respectively. The Danish model was found to have the best fit with the microwave drying process of CRES. Full article

(This article belongs to the Special Issue Comprehensive Utilization of Metallurgical Resources and Environmental Protection)

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Review

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21 pages, 5134 KiB

Open AccessReview

Valuable Recovery Technology and Resource Utilization of Chromium-Containing Metallurgical Dust and Slag: A Review

by Ju Xu, Mengke Liu, Guojun Ma, Dingli Zheng, Xiang Zhang and Yanglai Hou

Metals 2023, 13(10), 1768; https://doi.org/10.3390/met13101768 - 18 Oct 2023

Cited by 6 | Viewed by 2475

Abstract

As a type of metallurgical solid waste with a significant output, chromium-containing metallurgical dust and slag are gaining increasing attention. They mainly include stainless steel dust, stainless steel slag, ferrochrome dust, and ferrochrome slag, which contain significant amounts of valuable elements, such as [...] Read more.

As a type of metallurgical solid waste with a significant output, chromium-containing metallurgical dust and slag are gaining increasing attention. They mainly include stainless steel dust, stainless steel slag, ferrochrome dust, and ferrochrome slag, which contain significant amounts of valuable elements, such as chromium, iron, and zinc, as well as large amounts of toxic substances, such as hexavalent chromium. Achieving the harmless and resourceful comprehensive utilization of chromium-containing metallurgical dust and slag is of great significance to ensuring environmental safety and the sustainable development of resources. This paper outlines the physicochemical properties of stainless steel dust, stainless steel slag, ferrochrome dust, and ferrochrome slag. The current treatment technologies of chromium-containing metallurgical dust and slag by hydrometallurgy, the pyrometallurgical process, and the stabilization/solidification process are introduced. Moreover, the comprehensive utilization of resources of chromium-containing metallurgical dust and slag in the preparation processes of construction materials, glass ceramics, and refractories is elaborated. The aim of this paper is to provide guidance for exploring effective technology to solve the problem of chromium-containing metallurgical dust and slag. Full article

(This article belongs to the Special Issue Comprehensive Utilization of Metallurgical Resources and Environmental Protection)

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